66 PKOVISIONAL AID TO THE STUDY OF TASMANIA]* MOLLITSCA. 



Part 

 Rissoidse, xxxvi. 



Valvatidse, xxxviii. 



Part 

 Rissoidse, xxxvi. 



(S.) Fresh water or sub-aquatic, nearly all more or less covered 



with a dark brownish epidermis. 

 (a.) Spiral univalves. 

 * Sub-aquatic. 



Shell minute, cylindrical apex, truncated 

 whorls, striated transversely — 



margins of sea shore Truncatellidas, xxxix. 



Shell, smooth, elongated, perforated, 

 whorls very convex, aperture 

 round, peristome slightly ex- 

 panded or reflected, apex fre- 

 quently decollate. (Poinatiopsis) 

 ** Aquatic. 

 (1.) f Shellpery minute,depressed,conical 



or umbilicated 

 (2.) ff Shell very minute, 4 to 6 whorls, 

 sub-umbilicated, elongate, ovate or 

 pupif orm (Bithynella) , turbi- 

 nately ovate, inner lip more or 

 less reflected. (Beddomeia) 

 Shell minute, turbinately elongate, 

 sub-perforate. (Hydrobia.) 

 (3.) ftt Shell small, globosely rounded, 

 ovate imperforate, inner lip 

 thickened. (Brazieria.) 

 (4.) Shells found in or near brackish 

 water. Small, minute, globosely 

 conical, sharp lip 

 Shell, moderate, sub-globose, banded 

 Elongate, minute, pyramidal 

 pointed spire, flatfish whorls. 

 (Tatea.) 

 (5.) Shell moderate size or minute with 

 sharp spire more or less acumi- 

 nate; columella lip with oblique 

 plait above, oval,oblong, corneous 

 translucent, dextral. (Limnwa.) 

 Sinistral. (Physa.) 

 Shell very minute, discoidal 

 bi-concave. (Planorbis.) 



(b.) Non-spiral, pateliform or conical, 

 base, partly closed by a flat shelf, 

 leaving a semi-lunar aperture, 

 apex inclined to the right. 

 (Qundlachia.) 

 Shell aperture simple, entire, 

 conical, limpet-shaped, some- 

 times radiately ribbed. (Ancylus.) 



Assiminiidse, xxxvii. 

 AmphibolidEe, lxvi. 



Bissoellida3,xxxv. 



Part 



Limnseidse, lxv. 



Part 



Limnseidse, lxv. 



